The present invention relates to a color conversion filter substrate with good environmental resistance and high productivity for displaying multiple colors with high definition, and to an organic multicolor emitting display device provided with such a filter substrate. More specifically, the present invention relates to a color conversion filter substrate and an organic multicolor emitting display device provided with such a filter substrate for a display of electronic and electric equipment such as an image sensor, a personal computer, a word processor, a television, a fax machine, an audio equipment, a video equipment, a car navigation system, an electric desk top calculator, a telephone, a portable terminal, or an industrial instrument. Especially, the present invention relates to an organic multicolor emitting display device using a color conversion method.
In recent years, the information technology has been diversified. Display devices including solid imaging devices in the information technology have been required to have a better aesthetic appearance, a lighter weight, a thinner thickness and higher performance. A great effort has been made to reduce power consumption and increase a response speed. In particular, many attempts have been made to develop high-definition full-color display devices.
In the second half of the 1980s, an organic electro-luminescence (hereinafter referred to as xe2x80x98organic ELxe2x80x99) device with an organic molecule thin-layered structure has been developed as a device having higher contrast, constant-voltage driving, wider angle visibility, and faster response as opposed to a liquid crystal display device. Tang et al. reported that an organic EL formed of stacked thin films of organic molecules showed a high luminance of 1000 cd/m2 at an applied voltage of 10 V (Appl. Phys. Lett., 51, 913 (1987)). This stacked organic EL luminous device has excellent characteristics such as a wide view angle and a quick response time compared to liquid crystal display devices. After the report by Tang et al., a great effort has been made to develop organic EL luminous devices for a practical use. Attempts have also been made to develop similar devices composed of an organic polymer material.
Since the organic EL luminous device provides a high current density at a low voltage, it is expected to provide higher emission luminance and efficiency as opposed to inorganic EL luminous devices and LEDs. The organic EL display device is expected to have characteristics such as (1) high luminance and high contrast, (2) low driving voltage and high emission efficiency, (3) high resolution, (4) wide angle visibility, (5) high response speed, (6) possibility of increasing definition and providing color displays, (7) reduced weight and reduced thickness, and the like. Thus, the organic EL luminous device is expected to have a better aesthetic appearance, a lighter weight, a thinner thickness and higher performance.
Tohoku Pioneer Corporation has already developed products including vehicle-mounted green monochrome organic EL displays since November 1997. In order to meet the society needs, it is desirable to develop improved organic EL displays that are stable for an extended period of time, respond quickly, and display multiple colors or full colors with high definition.
There have been three major approaches as a method of displaying multiple or full colors with the organic EL display. One of the methods was disclosed in Japanese Patent Publications No. 57-167487, No. 58-147989, and No. 03-214593, in which light emitting elements of the three primary colors (red, green, and blue) are arranged in a matrix form. In this method, it is necessary to arrange three types of light-emitting materials (R, G, and B) in a matrix form with high precision, thereby making it technically difficult to produce and increasing a cost. Further, the three types of light-emitting materials have different life times, thereby shifting a color of the display with time.
As the second approach, in Japanese Patent Publications No. 01-315988, No. 02-273496, and No. 03-194895, a method in which a color filter and a backlight emitting white light are used to display the three primary colors through the filter was disclosed. However, it is difficult to obtain an organic light emitting device emitting the bright white light with a long life, which is necessary for obtaining bright three colors R, G, and B.
As the third approach, in recent years, a color conversion method has been proposed in which a filter is composed of a fluorescent material for absorbing light with a wavelength in a light-emission region of an organic light emitting device, so that the fluorescent material emits fluorescence with a wavelength in a visible light region (Japanese Patent Publications No. 03-152897 and No. 05-258860). In this approach, an organic light emitting device that emits a color other than white can be used. Therefore, it is possible to use an organic light emitting device with higher brightness as a light source. In a color conversion method using an organic light emitting device emitting blue light (Japanese Patent Publications No. 03-152897, No. 08-286033, and No. 09-208944), a frequency of blue light is converted to that of green or red light. A color conversion filter containing a fluorescent material with such color conversion effect may be formed in a high-resolution pattern. Accordingly, it is possible to provide a full-color light emitting display even with weak energy light such as near-ultraviolet light or visible light.
In order to form a pattern of a color conversion filter, a method in which a pattern is formed with a photolithography process after a film of a resist (photosensitive polymer) material containing fluorescent material is prepared by spin-coating has been disclosed in Japanese Patent Publications No. 05-198921 and No. 05-258860. Also, Japanese Patent Publication No. 09-208944 has disclosed a process in which a fluorescent material or fluorescent pigment is dispersed in a basic binder followed by etching the binder with an acid solution.
In general, it is important for a practical color display to possess high-resolution color and long-term stability (as described in Kinohzairyo Vol. 18, No. 2, 96). However, the organic EL luminous devices tend to markedly lose light-emission characteristics such as current-luminance characteristics after a specific period of time.
A major cause of the degraded light-emission characteristics is a growth of dark spots in the light-emitting layer. The dark spots are formed of light-emission defects. When the fluorescent material in the light-emitting layer is oxidized while using or storing the organic EL luminous device, the dark spots grow and spread over the entire light-emitting surface. It is believed that the dark spots are created by oxidation or aggregation of a material constituting a layered device caused by oxygen or moisture in the device. The dark spots grow not only when electricity is conducted but also during storage. In particular, it is believed that (1) the growth is accelerated by oxygen or moisture present around the device, (2) the growth is affected by oxygen or moisture attached to the organic stacked films, and (3) the growth is affected by moisture attached to parts or entered in the device when the device is manufactured.
As shown in FIG. 2, in the color conversion multicolor organic EL display, the color conversion filters 2, 3, and 4 are disposed under the transparent electrode 7. As described above, the color conversion filter is formed of a resin containing the colorant for color conversion. Because of thermal stability of the colorant, it is not possible to dry the color conversion filter at a temperature above 200xc2x0 C. Accordingly, it is likely that the color conversion filters contain moisture from a coating liquid or entered during a pattern-forming process. The moisture in the color conversion filters passes through the polymeric layer to the device while the device is stored or is continuously operated, thereby facilitating the growth of the dark spots.
In order to prevent moisture from entering the organic EL luminous device, Japanese Patent Publication No. 08-279394 has disclosed an approach in which an insulating inorganic oxide layer with a thickness of 0.01 to 200 xcexcm is provided between the color conversion filter layers and the organic EL luminous device. The inorganic oxide layer is required to have high moisture resistance for maintaining the life of the organic light-emitting layer. It is preferable that the inorganic oxide layer has coefficients of the gas permeability for both water vapor and oxygen less than 10xe2x88x9213 ccxc2x7cm/cm2xc2x7sxc2x7cmHg (according to the gas permeability test method in JIS K7126).
As disclosed in Japanese Patent Publication No. 07-146480 and No. 10-10518, in a method of forming the color filter, SiOx or SiNx is formed on a polymeric layer formed on the color filter layer with a DC sputtering, thereby improving adhesion of the transparent electrode layers. Japanese Patent Publication No. 2000-214318 has disclosed a method in which a low melting point glass is used. Also, Japanese Patent Publication No. 2000-223264 has disclosed a method in which a SiNx layer is formed with a CVD method to seal the organic EL luminous device from atmosphere.
In the color conversion type multicolor organic EL display, the inorganic film layer is required to have a permeability for the exciting light to efficiently transmit from the organic EL luminous device to the color conversion filter layers to reduce the power consumption and increase the lifetime.
In the color conversion type multicolor organic EL display, as shown in FIG. 2, an inorganic film layer, a polymeric film layer, and color conversion filter layers are disposed below transparent electrode layers. Light from an organic light-emitting layer passes through an interface between an organic layer and the transparent electrode layers, an interface between the transparent electrode layers and the inorganic film layer, and an interface between the inorganic film layer and the polymeric film layer, and reaches the color conversion filter layers. In general, light in the blue/green region of wavelength 450 to 500 nm is converted into blue, green and red light or the like. As the light from the organic light-emitting layer is reflected through interference at the above-mentioned interfaces in the device, an intensity of the transmitted light tends to fluctuate depending on a material and a thickness of each layer.
Consequently, to efficiently transmit the exciting light to the color conversion filter layers, it is necessary to provide an appropriate optical design for the inorganic film layer. The present invention has been accomplished in view of the problems described above, and it is an object of the present invention to provide a design for an inorganic film layer for efficiently transmitting the light from the organic EL luminous device, thereby obtaining a color conversion filter substrate and a multicolor organic EL display with stable light emission characteristics for a prolonged period of time.
Further objects and advantages of the invention will be apparent from the following description of the invention.
According to the first aspect of the present invention, a color conversion filter substrate comprises a transparent support substrate; a single type or a plurality of types of color conversion filter layers formed of a resin film containing a fluorescent colorant and formed on the support substrate in a desired pattern; a polymeric film layer formed of a transparent material for covering a surface of the support substrate on which the color conversion filter layers are formed and having a flat surface; a transparent inorganic film layer formed on the polymeric film layer; and a transparent electrode layer formed at an electrically independent region on the inorganic film layer. The inorganic film layer is formed of a single layer, and has a refractive index for light with a wavelength xcex in a range from 450 nm to 500 nm lower than that of the transparent electrode layer, and has a thickness d defined by nd=sxcex/2, wherein n is the refractive index of the inorganic film layer for the light with a wavelength Axcex, and s is a natural number.
According to the second aspect of the present invention, a color conversion filter substrate comprises a transparent support substrate; a single type or a plurality of types of color conversion filter layers formed of a resin film containing a fluorescent colorant and formed on the support substrate in a desired pattern; a polymeric film layer formed of a transparent material for covering a surface of the support substrate on which the color conversion filter layers are formed and having a flat surface; a transparent inorganic film layer formed on the polymeric film layer; and a transparent electrode layer formed at an electrically independent region on the inorganic film layer. The inorganic film layer is formed of at least double layers. One of the double layers adjacent to the transparent electrode has a refractive index for light with a wavelength A in a range from 450 nm to 500 nm lower than that of the transparent electrode layer. The inorganic film layer has (2p-1)th and (2p)th layers from the transparent electrode defined by n2p-1 greater than n2p, n2p-1d2p-1=s2p-1 xcex/2, and n2pd2p=s2p xcex/4, wherein p is a natural number, n is the refractive index of one layer in the inorganic film layer, d is the thickness of the one layer of the inorganic film layer, and s is a natural number.
According to the third aspect of the present invention, in the color conversion filter substrate according to the second aspect, the inorganic film layer is formed of layers having gradually decreasing refractive indexes for light with a wavelength xcex in a range from 450 nm to 500 nm from the transparent electrode layer toward the polymeric film layer.
According to the fourth aspect of the present invention, a color conversion filter substrate comprises a transparent support substrate; a single type or a plurality of types of color conversion filter layers formed of a resin film containing a fluorescent colorant and formed on the support substrate in a desired pattern; a polymeric film layer formed of a transparent material for covering a surface of the support substrate on which the color conversion filter layers are formed and having a flat surface; a transparent inorganic film layer formed on the polymeric film layer; and a transparent electrode layer formed at an electrically independent region on the inorganic film layer. The inorganic film layer is formed of at least double layers. One of the double layers adjacent to the transparent electrode has a refractive index for light with a wavelength xcex in a range from 450 nm to 500 nm lower than that of the transparent electrode layer. The inorganic film layer has (2p-1)th and (2p)th layers from the transparent electrode defined by n2p-1 less than n2p, n2p-1d2p-1=s2p-1 xcex/4, and n2pd2p=s2p xcex/2, wherein p is a natural number, n is the refractive index of one layer in the inorganic film layer, d is the thickness of the one layer in the inorganic film layer, and s is a natural number.
According to the fifth aspect of the present invention, a color conversion filter substrate comprises a transparent support substrate; a single type or a plurality of types of color conversion filter layers formed of a resin film containing a fluorescent colorant and formed on the support substrate in a desired pattern; a polymeric film layer formed of a transparent material for covering a surface of the support substrate on which the color conversion filter layers are formed and having a flat surface; a transparent inorganic film layer formed on the polymeric film layer; and a transparent electrode layer formed at an electrically independent region on the inorganic film layer. The inorganic film layer is formed of a single layer having gradually decreasing refractive indexes from the transparent electrode layer toward the polymeric film layer.
According to the sixth aspect of the invention, in the color conversion filter substrate according to the first to fifth aspects, the transparent electrode layer has a thickness d. Relative to a wavelength xcex between 450 nm and 500 nm, the thickness d is defined by nd=sxcex/2, wherein n is a refractive index of the transparent electrode layer for light with the wavelength xcex, and s is a natural number.
According to the seventh aspect of the present invention, a color conversion type multicolor display includes a light-emitting layer containing a light-emitting-material and the second electrode layer formed in this order on the color conversion filter substrate according to any of the first to sixth aspect.
According to the eighth aspect of the present invention, a method of manufacturing a color conversion filter substrate comprises the steps of: preparing a transparent support substrate; forming a single type or a plurality of types of color conversion filter layers formed of a resin film containing a fluorescent colorant on the support substrate in a desired pattern; forming a polymeric film layer formed of a transparent material for covering a surface of the support substrate on which the color conversion filter layers are formed, and having a flat surface; forming a transparent inorganic film layer on the polymeric film layer; and forming a transparent electrode at an electrically independent region on the inorganic film layer. The inorganic film layer is formed of a single layer, and has a thickness d. Relative to a wavelength xcex between 450 nm and 500 nm, the thickness d is defined by nd=sxcex/2, wherein n is a refractive index of the inorganic film layer for light with the wavelength xcex, and s is a natural number. The transparent electrode layer has a refractive index higher than that of the inorganic film layer.
According to the ninth aspect of the present invention, a method of manufacturing a color conversion filter substrate comprises the steps of: preparing a transparent support substrate; forming a single type or a plurality of types of color conversion filter layers formed of a resin film containing a fluorescent colorant on the support substrate in a desired pattern; forming a polymeric film layer formed of a transparent material for covering a surface of the support substrate on which the color conversion filter layers are formed, and having a flat surface; forming a transparent inorganic film layer on the polymeric film layer; and forming an transparent electrode at an electrically independent region on the inorganic film layer. The inorganic film layer is formed of at least double layers. One of the double layers adjacent to the transparent electrode has a refractive index for light with a wavelength xcex in a range from 450 nm to 500 nm lower than that of the transparent electrode layer. The inorganic film layer has (2p-1)th and (2p)th layers from the transparent electrode defined by n2p-1 greater than n2p, n2p-1d2p-1=s2p-1 xcex/2, and n2pd2p=s2p xcex/4, wherein p is a natural number, n is the refractive index of one layer in the inorganic film layer, d is the thickness of the one layer of the inorganic film layer, and s is a natural number. The transparent electrode layer has a refractive index higher than that of the inorganic film layer.
According to the tenth aspect of the present invention, in the method of manufacturing the color conversion filter substrate according to the ninth aspect, the inorganic film layer has gradually decreasing refractive indexes for light with a wavelength xcex in a range from 450 nm to 500 nm from the transparent electrode layer toward the polymeric film layer.
According to the eleventh aspect of the present invention, a method of manufacturing a color conversion filter substrate comprises the steps of: preparing a transparent support substrate; forming a single type or a plurality of types of color conversion filter layers formed of a resin film containing a fluorescent colorant on the support substrate in a desired pattern; forming a polymeric film layer formed of a transparent material for covering a surface of the support substrate on which the color conversion filter layers are formed, and having a flat surface; forming a transparent inorganic film layer on the polymeric film layer; and forming a transparent electrode at an electrically independent region on the inorganic film layer. The inorganic film layer is formed of at least double layers. One of the double layers adjacent to the transparent electrode has a refractive index for light with a wavelength xcex in a range from 450 nm to 500 nm lower than that of the transparent electrode layer. The inorganic film layer has (2p-1)th and (2p)th layers from the transparent electrode defined by n2p-1 less than n2p, n2p-1d2p-1=s2p-1 xcex/4, and n2pd2p=s2p xcex/2, wherein p is a natural number, n is the refractive index of one layer in the inorganic film layer, d is the thickness of the one layer of the inorganic film layer, and s is a natural number. The transparent electrode layer has a refractive index higher than that of the inorganic film layer.
According to the twelfth aspect of the present invention, a method of manufacturing a color conversion filter substrate comprises the steps of: preparing a transparent support substrate; forming a single type or a plurality of types of color conversion filter layers formed of a resin film containing a fluorescent colorant on the support substrate in a desired pattern; forming a polymeric film layer formed of a transparent material for covering a surface of the support substrate on which the color conversion filter layers are formed, and having a flat surface; forming a transparent inorganic film layer on the polymeric film layer; and forming a transparent electrode at an electrically independent region on the inorganic film layer. The inorganic film layer has a structure having continuously changed compositions. The transparent electrode layer has a refractive index higher than that of the inorganic film layer.
According to the thirteenth aspect of the present invention, a method of manufacturing a color conversion type multicolor display comprises the steps of: preparing a transparent support substrate; forming a single type or a plurality of types of color conversion filter layers formed of a resin film containing a fluorescent colorant on the support substrate in a desired pattern; forming a polymeric film layer formed of a transparent material for covering a surface of the support substrate on which the color conversion filter layers are formed, and having a flat surface; forming a transparent inorganic film layer on the polymeric film layer; forming a transparent electrode at an electrically independent region on the inorganic film layer; forming an organic light-emitting layer containing a light-emitting material on the transparent electrode layer; and forming the second electrode layer on the organic light-emitting layer. The inorganic film layer is formed of a single layer, and has a thickness d. Relative to a wavelength xcex between 450 nm and 500 nm, the thickness d is defined by nd=sxcex/2, wherein n is a refractive index of the inorganic film layer for light with the wavelength xcex, and s is a natural number. The transparent electrode layer has a refractive index higher than that of the inorganic film layer.
According to the fourteenth aspect of the present invention, a method of manufacturing a color conversion type multicolor display comprises the steps of: preparing a transparent support substrate; forming a single type or a plurality of types of color conversion filter layers formed of a resin film containing a fluorescent colorant on the support substrate in a desired pattern; forming a polymeric film layer formed of a transparent material for covering a surface of the support substrate on which the color conversion filter layers are formed, and having a flat surface; forming a transparent inorganic film layer on the polymeric film layer; forming a transparent electrode at an electrically independent region on the inorganic film layer; forming an organic light-emitting layer containing a light-emitting material on the transparent electrode layer; and forming the second electrode layer on the organic light-emitting layer. The inorganic film layer is formed of at least double layers. One of the double layers adjacent to the transparent electrode has a refractive index for light with a wavelength A in a range from 450 nm to 500 nm lower than that of the transparent electrode layer. The inorganic film layer has (2p-1)th and (2p)th layers from the transparent electrode defined by n2p-1 greater than n2p, n2p-1d2p-1=s2p-1 xcex/2, and n2pd2p=s2p xcex/4, wherein p is a natural number, n is the refractive index of one layer of the inorganic film layer, d is the thickness of the one layer of the inorganic film layer, and s is a natural number. The transparent electrode layer has a refractive index higher than that of the inorganic film layer.
According to the fifteenth aspect of the present invention, in the method of manufacturing the color conversion type multicolor display according to the fourteenth aspect, the inorganic film layer gradually decreases refractive indexes for light with a wavelength xcex in a range from 450 nm to 500 nm from the transparent electrode layer toward the polymeric film layer.
According to the sixteenth aspect of the present invention, a method of manufacturing a color conversion type multicolor display comprises the steps of: preparing a transparent support substrate; forming a single type or a plurality of types of color conversion filter layers formed of a resin film containing a fluorescent colorant on the support substrate in a desired pattern; forming a polymeric film layer formed of a transparent material for covering a surface of the support substrate on which the color conversion filter layers are formed, and having a flat surface; forming a transparent inorganic film layer on the polymeric film layer; forming a transparent electrode at an electrically independent region on the inorganic film layer; forming an organic light-emitting layer containing a light-emitting material on the transparent electrode layer; and forming the second electrode layer on the organic light-emitting layer. The inorganic film layer is formed of at least double layers. One of the double layers adjacent to the transparent electrode has a refractive index for light with a wavelength xcex in a range from 450 nm to 500 nm lower than that of the transparent electrode layer. The inorganic film layer has (2p-1)th and (2p)th layers from the transparent electrode defined by n2p-1 less than n2p, n2p-1d2p-1=s2p-1 xcex/4, and n2pd2p=s2p xcex/2, wherein p is a natural number, n is the refractive index of the one layer of the inorganic film layer, d is the thickness of the one layer of the inorganic film layer, and s is a natural number. The transparent electrode layer has a refractive index higher than that of the inorganic film layer.
According to the seventeenth aspect of the present invention, a method of manufacturing a color conversion type multicolor display comprises the steps of: preparing a transparent support substrate; forming a single type or a plurality of types of color conversion filter layers formed of a resin film containing a fluorescent colorant on the support substrate in a desired pattern; forming a polymeric film layer formed of a transparent material for covering a surface of the support substrate on which the color conversion filter layers are formed, and having a flat surface; forming a transparent inorganic film layer on the polymeric film layer; forming a transparent electrode at an electrically independent region on the inorganic film layer; forming an organic light-emitting layer containing a light-emitting material on the transparent electrode layer; and forming the second electrode layer on the organic light-emitting layer. The inorganic film layer has a structure having continuously changed compositions. The transparent electrode layer has a refractive index higher than that of the inorganic film layer.